High-Temperature Reaction Between Cemented Tungsten Carbide and Copper

Interdiffusion in the system cemented tungsten carbide-molten copper has been studied in the range ≤1120°C with special emphasis on the effects of WC grain size and Co content. Techniques used for analyzing the diffusion layers obtained are EPMA, optical microscopy, and microhardness measurement. A Cu-bonded WC layer develops with simultaneous diffusion of Co from the cemented carbide into the bulk copper. The Cu-bonded WC layer grows until a Co-rich layer forms at the Cu/WC-Co interface; further heating pushes the Cu-bonded WC layer deep into the bulk cemented carbide without any significant change in layer thickness. When the WC grain size is reduced and the cobalt content increased, the penetration of copper into cemented carbides increases. A tentative mechanism of interdiffusion has been proposed based on the experimental results.     

Mutagenic Activity of Heat-Induced Cholesterol-Degradation Products

Mutagenic activities of degradation products from pure crystalline cholesterol by heat-treatment in air were examined with a streptomycin-dependent strain from the Salmonella typhimurium TA98. Heatings at 225°C for periods of over 5 hr or at temperatures above 150°C for 7 hr were required for mutagens to be detected.     

On the estimation of noise covariances in linear discrete-time systems

This paper is concerned with an approach for estimating or tracking the time-varying input and measurement noise covariances in time-varying discrete-time linear systems. The approach is firstly to introduce the estimators for the case where the noise co-variances are unknown constants. (The estimators are defined as the mean squares of the estimators of noises based on all the available measurement data.) They arc then transformed in sequential form, and are subsequently modified by incorporating a fading memory to yield estimates for time-varying noise covariances. The time-varying noise covariance estimates are evaluated as the fading mean squares of the estimates of noises based on all the measurement data up to present time. A numerical example for a simple system indicates acceptable performance of the proposed method.     

A possibility for new evaluating method of cytotoxicity by using heat shock protein assay

To determine whether heat shock proteins can be utilized as a biomarker for cytotoxicity of dental materials the induction of synthesis of heat shock proteins by mercuric chloride was examined. To analyse the synthesis of heat shock proteins, HeLa cells were labelled with [35S] methionine, and the labelled proteins were separated by SDS-PAGE and autoradiographed. Incubation of the cells in a medium containing 1.25 to 40 M mercuric chloride markedly increased the synthesis of HSP70. At 20 or 40 M mercuric chloride in medium, HeLa cells synthesized HSP70 at 2 h after exposure, maximally at 4–7 h, and gradually diminished thereafter. Examination of the cytotoxicity of mercuric chloride by the conventional neutral red uptake assay revealed a reduction of uptake of the dye in the presence of mercuric chloride at 40 M and above. These findings suggest that the induction of synthesis of HSP70 is one of the most sensitive cellular responses caused by mercury ion, and the heat shock protein assay can be utilized for evaluation of the cytotoxicity of dental materials.     

Optimal production planning for a multiproduct,multistage production system

A mathematical model of production planning for a multiproduct, multistage produetionaystom (production equation, transition equation and objective function) was constructed in order to derive the optimal decision rule to be adapted to demand fluctuation. With this model the optimal solution and the computational algorithm were determined by functional space approach. With use of this algorithm, a numerical example of optimal production planning was solved.     

Conditions for the delay-independent stabilization and the decay rate assignability of linear systems

In a previous paper (Amemiya 1983) two sufficient conditions were introduced for the delay-independent stabilization of linear systems by means of state-variable feedback including no delays.

In this paper the concept of delay-independently upper or lower bound of decaying rate assignability (DIUDA or DILDA) are introduced and it is proved that the two conditions previously obtained are necessary and sufficient condition for DIUDA and necessary condition for DILDA of linear systems by means of state-variable feedback including no delays. The conditions obtained are also applicable to systems including time-varying delays.     

Analytical Simulation of the Passive Solar System

The computer simulation is a useful tool for heat transfer analysis of the passive solar systems especially in preliminary performance evaluation, implementation, and/or optimization of the system configurations in the course of the development and constructive design.

The present article describes advantages and conditions of an application of the simulation scheme to the passive solar system analysis, along with design criterion and requirements for analytical heat transfer models for the passive solar system simulations.

A state-of-the-art program, ESPAR, used for the simulations, has been developed for the elementary heat transfer analysis of the passive solar systems constructed as a part of a single room residential building, and formulated around a finite differential heat conductive model combined with typical passive solar system submodels.

Analytical results by ESPAR for the direct gain system with sensible or latent heat storage wall and Trombe wall system are presented comparatively with measured results.     

A STRATEGY FOR THE DEVELOPMENT OF NEW ENERGY TECHNOLOGY IN THE GLOBAL ENVIRONMENT ERA (The Revised Sunshine Project)

The Japanese R & D Programme on solar energy under the Sunshine Project of MITI will be described. The programme is aiming at practical use of solar energy in the 21st century.     

The fabrication and properties of aesthetic FRP wires for use in orthodontics

Transparent or translucent fibre-reinforced polymeric wires have been produced in an attempt to reproduce the mechanical properties of the metallic wires in current use in orthodontics. Two methods were employed: mould polymerization, and hot-drawing. Both methods produced wires of 0.5 mm diameter. Two polymers were investigated, poly(methyl methacrylate) and epoxy resin, and these were filled with either long silane-coated alumina fibres or fibres made from CPSA glass. Whilst mould-polymerized wires showed a linear increase in Young's modulus with fibre content, they did not obey the rule of mixtures. However, the hot-drawn wires did, and they also demonstrated the rigidity, strength and good elastic recovery needed for use in orthodontics.